I sold 1 item, why am I being charged a monthly selliers fee?

[chillibite]

I sold 1 item on eBay last month, and now I've recived a monthly invoice for seller fees. I was anticipating paying some kind of fee to sell, but was under the impression it would be taken Off the final sale price for the item ( as it was the last time I sold something like 5 years ago). Why am a being charged a monthly fee for selling 1 item, and how do I stop the fees?